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December 21, 2010

Future Generations Threatened With Biological Invasions

by Sam Savage

Animals and plants introduced from foreign habitats may not seem harmful and can coexist with native species for decades, according to a European study published Monday.

Species that are taken away from their natural predators and placed elsewhere can disrupt native species in their new habitats, and scientists say the problem is already costing Europe $16 billion per year.

The study, published in the US Proceedings of the National Academy of Sciences, which is likely to hold true for other continents as well, means that the seeds of future problems have already been sewn.

The study compared the effects of "alien species" such as American Ragweed, Canadian Geese and Japanese Deer in 28 European countries. The findings indicated that it can be decades before experts can determine which alien species will be disruptive, and studying those that arrived in 1990 was a good indicator of current problems than looking at those from 2000.

"This lag in the cause-and-effect relationship would mean that ... the seeds of future invasion problems have already been sown," the study said.

Birds and insects were quickest to become established in new habitats, aided by their mobility. Other species took far longer to reach critical numbers to become invasive.

Introduced species to Europe from the 1800s include ragweed, whose pollen is blamed for hay fever, and the black locust tree, which can damage grasslands by storing nitrogen.

Trade and travel increases during the past 100 years or more means that problems are likely to worsen unless checks on everything from tanks and hulls of ships to coffee grain imports are more greatly imposed.

"We should do more about this problem now," Stefan Dullinger, of the University of Vienna, Austria, told Reuters.

"Otherwise, things can become even much worse than they are in a few decades," said Dullinger, who was among the authors of the study from institutes in New Zealand, the Czech Republic, Germany, Switzerland, Spain, Italy and France.

The study also recommended that Europe should target controls at animal and plant species that were so far causing no damage but were known to be invasive in other habitats.

Dullinger said climate change could also add to the spread of invasive species. "Warmer temperatures could trigger the spread of invasive species that are limited by climate now."

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Image Caption: Common Ragweed (Ambrosia artemisiifolia) is the most widespread plant of the genus Ambrosia in North America. Its wind-dispersed pollen is a strong allergen to many people with hay fever. Credit: Klaus-Dieter Sonntag/ fotoplusdesign.de